1. Field of the Invention
This invention relates generally to local area networks (LANs) and more particularly to apparatus and to a method for determining the location of a network node or component from the interaction of the network node with the local area network.
2. Description of the Related Art
For certain types of local area networks, such as the Carrier Sense Multiple Access/Collision Detect (CSMA/CD) architecture, as defined by the IEEE 802.3, a multiplicity of devices can be coupled to a (cable) segment of the local area network. For example, a segment can consist of a coaxial cable segment 500 meters in length. A local area network can include a plurality of cable segments, each cable segment coupled by a repeater unit (to compensate losses experienced by propagation along the cable) to other cable segments and each cable segment having up to 1024 system members coupled thereto. The system members are coupled to the coaxial cable by means of a device typically referred to as a tap. The tap is a unit that clamps onto the coaxial cable, pushes aside the braided grounding wire, and forces a small pin into the central conducting element to detect signals transmitted on the central conducting element. Referring now to FIG. 1, the typical configuration of a system member coupled to the cable segment is shown. The tap and transceiver unit 12 are coupled to the coaxial cable segment 11. The tap portion physically couples to cable segment, while the transceiver portion encodes signals that are going to be applied to the cable segment 11 in the specified local area network format and decodes signals received from the cable segment 11. The network interconnect unit 14 is coupled to the tap and transceiver unit 12 and provides the data link protocols specific to the local area network. The network interconnect unit 14 typically provides power for the tap and transceiver unit 12 through the same conducting leads that carry the signals. The network interconnect unit 14 is typically contained within a data processing system 15, the data processing system 15 being generally referred to as a network node.
Data is transferred between local area network system members over at least one cable segment. The data is typically transferred in groups of signals referred to as packets. The packets, in addition to the information conveyed therein, include a plurality of identifying fields such as a field identifying the source local area network system member and a field identifying the target local area network member. The presence of the field specifying the source of the data packet in the packet itself is important to the operation of the invention disclosed herein.
Because the length of the cable segment cam make visual inspection inconvenient or impossible and because the ease of moving the network components limits the usefulness of an inventory of network locations of systems members, a need has therefore been felt for apparatus and for a method that can determine the location of network components automatically form apparatus coupled to the local area network.